An apparatus and a method for diagnosing an internal combustion engine for a vehicle, the apparatus encompassing: a recognition device that is embodied to recognize a shutoff operation of the internal combustion engine while the vehicle is being operated in particular in a normal operating mode; a detection device that is embodied to detect, during the shutoff operation, a part or several parts of a curve for a rotation speed or an inter-tooth time of a crankshaft of the internal combustion engine; a comparison device that is embodied to compare at least one feature of the part or the several parts of the curve, in a comparison, with a comparison feature; and a diagnostic device that is embodied to perform, as a function of a result of the comparison, a diagnosis with regard to a compression loss in at least one cylinder.